I've used it both to lap the barrel in my 22-250, and to deep clean and recondition the barrel of my Knight DISC.

I found that the end result of lapping the 22-250 barrel (Ruger M77VT MkII) was that patches went through noticibly smoother, and bore cleaning is an easy 5 minute process that rarily requires the use of a bore brush. Just a couple solvent patches, wait a couple minutes, and then dry patches until they come out clean. Further cleaning does not yield any further fouling. There is also no significant copper buildup in the bore, even shooting 45 grain loads that I clocked with my Chrony at a mean of 4065fps at 15ft.

I also decided to try it on my muzzleloaders barrel when I started to see accuracy degrade and become erratic with seemingly no cause with already proven loads. I thought that maybe my scope was dead, so I got a new one, but that didn't help. I've always thought that soap 'n' water cleaning did a thourough enough job, and I could see no visible fouling in the bore after cleaning, but I decided to go ahead and lap it with JB Bore Paste anyway. Apparently a fouled barrel was the culprit, because the next trip to the range I was seeing the same accuracy I had had before.

I think it's good stuff myself. And I don't think that it damages a barrel in any way. The stuff is mildly abrasive, by I don't think that the abrasive compounds are anywhere near hard enough to do anything more than clean out soft deposits and polish the bore at the microscopic level.

Mike